The gas mixing system is protected from failure or mis-setting of the primary pressure regulators (the ones mounted on the manifolds on the exterior of the gas shed - near the bottles) by hidden regulators mounted just inside the gas shed. It is these regulators which actually set the maximum supply pressure to the mixing valves. These regulators should never be adjusted by other than a gas system expert! The nominal secondary pressure supplied by both the argon and ethane secure regulators is 15 psig.